Genetics and Evolution
- Broad palm with single palm crease is visible in a person suffering from- Answer: 2. Down's syndrome Key idea: Down's syndrome (trisomy 21) has typical physical features. These include a short stature, a small roun... 1
- Which one of the following symbols represents mating between relatives in human pedigree analysis? Answer: 3. [pedigree symbol: square joined to circle by double line] Key idea: In a human pedigree, a double horizontal line between the mal... 1
- Match List I with List II.List I: A. Gene 'a'; B. Gene 'y'; C. Gene 'i'; D. Gene 'z'List II: I. β-galactosidase; II. Transacetylase; III. Permease; IV. Repressor proteinChoose the correct answer from the options given below: Answer: 3. A-II, B-III, C-IV, D-I Key idea: In the lac operon, each gene codes for a specific protein. Gene i codes for the repressor protei... 1
- Which of the following statements are correct about Klinefelter's Syndrome?A. This disorder was first described by Langdon Down (1866).B. Such an individual has overall masculine development. However, the feminine development is also expressed.C. The… Answer: 4. B and E only Key idea: Klinefelter's syndrome has the karyotype 47, XXY. A is wrong: Langdon Down described Down syndrome. B is c... 1
- The phenomenon of pleiotropism refers to Answer: 4. a single gene affecting multiple phenotypic expression. Key idea: Pleiotropy is the effect of a single gene on multiple phenotypi... 1
- Unequivocal proof that DNA is the genetic material was first proposed by Answer: 3. Alfred Hershey and Martha Chase Key idea: Hershey and Chase (1952) gave the unequivocal proof that DNA is the genetic material. T... 1
- Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by Answer: 4. Alfred Sturtevant Key idea: Alfred Sturtevant, a student of T. H. Morgan, used the frequency of recombination between gene pairs... 1
- The recombination frequency between the genes a & c is 5%, b & c is 15%, b & d is 9%, a & b is 20%, c & d is 24% and a & d is 29%. What will be the sequence of these genes on a linear chromosome ? Answer: 1. a, c, b, d Key idea: Higher recombination frequency means a greater distance between genes. The farthest pair sits at the ends. T... 1
- Ten E.coli cells with ^15N - dsDNA are incubated in medium containing ^14N nucleotide. After 60 minutes, how many E.coli cells will have DNA totally free from ^15N ? Answer: 4. 60 cells Key idea: DNA replication is semi-conservative, and the question assumes the usual E. coli doubling time of 20 minutes.... 1
- If a colour blind female marries a man whose mother was also colour blind, what are the chances of her progeny having colour blindness ? Answer: 1. 100% Key idea: Colour blindness is X-linked recessive. The female is colour blind: X^cX^c . The man's mother was colour blind, so... 1
- If the length of a DNA molecule is 1.1 metres, what will be the approximate number of base pairs ? Answer: 2. 3.3×10⁹ bp Key idea: Distance between two base pairs is 0.34\ nm = 0.34×10⁻⁹ m. N = dfrac1.10.34×10⁻⁹ ≈ 3.2×10⁹ ≈ 3.3×10⁹ bp, whi... 1
- In an E.coli strain i gene gets mutated and its product can not bind the inducer molecule. If growth medium is provided with lactose, what will be the outcome ? Answer: 4. z, y, a genes will not be translated Key idea: If the repressor (product of the i gene) cannot bind the inducer, it stays bound t... 1
- If a geneticist uses the blind approach for sequencing the whole genome of an organism, followed by assignment of function to different segments, the methodology adopted by him is called as : Answer: 2. Sequence annotation In the sequence annotation approach, the whole genome is sequenced blindly and functions are assigned to segm... 1
- Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).Assertion (A) :Mendel's law of Independent assortment does not hold good for the genes that are located closely on the same chromosome.Reason (R… Answer: 4. (A) is correct but (R) is not correct Assertion: genes close together on the same chromosome are linked and tend to be inherited... 1
- Which of the following occurs due to the presence of autosome linked dominant trait ? Answer: 3. Myotonic dystrophy Myotonic dystrophy is an autosomal dominant disorder. Thalassemia and sickle cell anaemia are autosomal recess... 1
- Given below are two statements :Statement I :Mendel studied seven pairs of contrasting traits in pea plants and proposed the Laws of InheritanceStatement II :Seven characters examined by Mendel in his experiment on pea plants were seed shape and colo… Answer: 2. Both Statement I and Statement II are correct Mendel studied seven pairs of contrasting traits in pea and proposed the laws of in... 1
- XO type of sex determination can be found in : Answer: 4. Grasshoppers XO sex determination (male has one X, female XX) is found in grasshoppers. Monkeys and Drosophila have XY males, and... 1
- The process of translation of mRNA to proteins begins as soon as : Answer: 2. The small subunit of ribosome encounters mRNA Translation begins when the small ribosomal subunit binds to the mRNA. Then the ini... 1
- DNA polymorphism forms the basis of : Answer: 4. Both genetic mapping and DNA finger printing DNA polymorphism means variation in DNA sequence between individuals. It is the basi... 1
- Statement I :The codon ‘AUG’ codes for methionine and phenylalanine.Statement II :‘AAA’ and ‘AAG’ both codons code for the amino acid lysine.In the light of the above statements, choose the correct answer from the options given below. Answer: 4. Statement I is incorrect but Statement II is true Statement I is false: AUG codes only for methionine (it is also the start codon... 1
- Persons with ‘AB’ blood group are called as "Universal recipients". This is due to : Answer: 4. Absence of antibodies, anti-A and anti-B, in plasma AB blood group has antigens A and B on RBCs but has no anti-A or anti-B antib... 1
- If Adenine makes 30% of the DNA molecule, what will be the percentage of Thymine, Guanine and Cytosine in it ? Answer: 3. T : 30 ; G : 20 ; C : 20 By Chargaff's rule A = T and G = C. A = 30% so T = 30%. A + T = 60%, leaving 40% for G + C, so G = C = 2... 1
- Which one of the following statements about Histones is wrong ? Answer: 2. The pH of histones is slightly acidic. Histones are rich in basic amino acids lysine and arginine, which carry positive charge, s... 1
- In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased ? Answer: 3. 25% Both parents are heterozygous carriers (Hb ^A Hb ^S ). Cross: Hb ^A Hb ^S × Hb ^A Hb ^S gives 1 Hb ^A Hb ^A : 2 Hb ^A Hb ^S :... 1